Alkali metal group trends

It is possible to explain these trends in terms of the electron configurations of the corresponding atoms. Consider first the increase in radius observed as we move down the table, let us say among the alkali metals (Group 1). All these elements have a single s electron outside a filled level or filled p sublevel. Electrons in these inner levels are much closer to the nucleus than the outer s electron and hence effectively shield it from the positive charge of the nucleus. To a first approximation, each inner electron cancels the charge of one pro-... 

The alkali metals form a homogeneous group of extremely reactive elements which illustrate well the similarities and trends to be expected from the periodic classification, as discussed in Chapter 2. Their physical and chemical properties are readily interpreted in terms of their simple electronic configuration, ns, and for this reason they have been extensively studied by the full range of experimental and theoretical techniques. Compounds of sodium and potassium have been known from ancient times and both elements are essential for animal life. They are also major items of trade, commerce and chemical industry. Lithium was first recognized as a separate element at the beginning of the nineteenth eentury but did not assume major industrial importance until about 40 y ago. Rubidium and caesium are of considerable academic interest but so far have few industrial applications. Francium, the elusive element 87, has only fleeting existence in nature due to its very short radioactive half-life, and this delayed its discovery until 1939. 

The Group 2 or alkaline earth metals exemplify and continue the trends in properties noted for the alkali metals. No new principles are involved, but the ideas developed in the preceding chapter gain empha.sis and clarity by their further application and extension. Indeed, there is an impressively close parallelism between the two groups as will become increasingly clear throughout the chapter. 

The predominantly ionic alkali metal sulfides M2S (Li, Na, K, Rb, Cs) adopt the antifluorite structure (p. 118) in which each S atom is surrounded by a cube of 8 M and each M by a tetrahedron of S. The alkaline earth sulfides MS (Mg, Ca, Sr, Ba) adopt the NaCl-type 6 6 structure (p. 242) as do many other monosulfides of rather less basic metals (M = Pb, Mn, La, Ce, Pr, Nd, Sm, Eu, Tb, Ho, Th, U, Pu). However, many metals in the later transition element groups show substantial trends to increasing covalency leading either to lower coordination numbers or to layer-lattice structures. Thus MS (Be, Zn, Cd, Hg) adopt the 4 4 zinc blende structure (p. 1210) and ZnS, CdS and MnS also crystallize in the 4 4 wurtzite modification (p. 1210). In both of these structures both M and S are tetrahedrally coordinated, whereas PtS, which also has 4 4... 

This article summarizes the chemistry of alkali metals with group 14, 15, and 16 ligands with specific emphasis on structure and bonding. With several excellent, recent review articles in the area, we focus specifically on newer developments, with already reviewed material only mentioned briefly to show trends and connections. 

The alkaline earth metals undergo the same kinds of redox reactions that the alkali metals do, but they lose two electrons rather than one to yield dipositive ions, M2+. Because their first ionization energy is larger than that of alkali metals (Figure 6.3), the group 2A metals tend to be somewhat less reactive than alkali metals. The general reactivity trend is Ba > Sr > Ca > Mg > Be. 

Table Group-1 Elements Alkali Metals Increasing Decreasing Exceptions Trends Trends...

Table I lists the measured frequency changes for all of the metals we have studied. It is Interesting to compare the trends in Av2 within groups. The alkali metal interaction clearly...

The synthesis, structures, and reactions of silicon-substituted alkyl derivatives of metals from groups 1, 2, and 3 have been recently reviewed. A diverse range of structures has been discovered with the alkali metals. More recently, some additional structures and an important discussion of structural trends observed among the silicon-substituted alkyl derivatives of the alkali metals have also been published. " Tris(trimethylsilyl)methyl lithium forms a solvent-free dimer, as well as several ate complexes in the presence of bases (THF or TMEDA). In the alkyl-bridged dimer of tris(trimethylsilyl)methyl lithium (2), there are interactions between the C-H bonds of the silyl ligand and the lithium atoms (3) (Li to C distances of 254.1(7) and 246.6(6) pm). ... 

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